The need for a device which provides a source of direct current electricity is well known throughout the electronics world, especially in the telecommunications, chemical, automotive, and computer industries, and in research and development laboratories of diverse types. Any such device is generally termed a direct current power supply; it may stand alone as an instrument, or it may incorporated inside some system.
The present invention is a dc power supply configuration of the voltage regulating type. It has been implemented using linear integrated circuits and a few discrete components.
Integrated circuits have been invented for power supply applications wherein a high degree of regulation, low cost, noise rejection, output current limitation, and ease of implementation have been achieved. The industry standard type number LM723, described in the LINEAR DATA BOOK cited above, p 1-96, is one such circuit. Complete power circuit configurations are given on pp 1-99 & 1-100 of this reference. Another such integrated circuit is described in U.S. Pat. No. 4,413,226.
Power supplies which can produce a regulated emf between zero and two volts have been invented and are now particularly easy to implement using zero sensing operational amplifiers, such as the industry standard type #LM2904 (Linear Data Book, op cit, p 3-153), which is a junction transistor integrated circuit device. (An operational amplifier is herein said to be zero sensing if it can function with a common mode input emf equal to the most negative emf in the amplifier). Similar applications have been made of a recently developed integrated circuit employing field effect transistors. (LINEAR INTEGRATED CIRCUITS, loc cit, Type #CA3130, p 280).
In all of the aforementioned power supply circuits there remain the problems of errors due to input offsets intrinsic to the operational amplifiers and no provision for indicating to the operator when the power supply is not really delivering to its output terminal the voltage selected by the operator.